Catalytic system based on a rare-earth metallocene and a co-catalyst having a plurality of carbon-magnesium bonds

ABSTRACT

A catalytic system based on at least one rare-earth metallocene and as co-catalyst an organomagnesium reagent of formula X—Mg—R A —Mg—X is provided. In the formula, R A  is a divalent aliphatic hydrocarbon-based chain, optionally interrupted with an oxygen atom, a sulfur atom or with an arylene group, and X is a halogen atom. The catalytic system allows the synthesis of dienic and/or ethylenic telechelic polymers.

This U.S. patent application is a national phase entry of international patent application no. PCT/FR2021/052045, filed Nov. 19, 2021, which claims priority to French patent application no. FR2012080, filed Nov. 24, 2020, the entire contents of which are incorporated herein by reference in their entirety.

BACKGROUND 1. Technical Field

The field of the present invention is that of catalytic systems that may be used in the preparation of telechelic polyolefins.

2. Related Art

The synthesis of polyolefins by polymerization of an olefin in the presence of a catalytic system comprising a rare-earth metallocene and a co-catalyst is well known. The co-catalyst is used to activate the metallocene for polymerization. The co-catalyst may be an organolithium, organomagnesium or organoaluminium reagent, for instance as described in patent applications EP 1 092 731, WO 2004/035639, WO 2007/054224 and WO 2018/224776. When the co-catalyst is an organomagnesium reagent, it is typically an organomagnesium chloride or an organomagnesium reagent in which the magnesium atom is bonded to two aliphatic groups, such as dibutylmagnesium, butylethylmagnesium and butyloctylmagnesium.

It is also known that the synthesis of functional polyolefins from these catalytic systems requires a functionalization step. This functionalization step is subsequent to the polymerization reaction and is performed by adding a modifying agent, generally at the end of the polymerization. This first method allows the functionalization of only one chain end of the polymer. An alternative to this first method was to propose the use of functional transfer agents instead of co-catalysts. These functional transfer agents described in patent applications WO 2016/092237 and WO 2013/135314 are, for example, organomagnesium reagents bearing an amine, ether or vinyl function. This alternative indeed makes it possible to omit the additional functionalization step after the polymerization reaction to form functional polymers. However, this alternative leads, like the first method, to the functionalization of only one chain end of the polymer, unless an additional functionalization step is performed at the end of the polymerization. There is therefore concern to find a solution that allows the preparation of polyolefins that are functionalized at both of their ends in a process that is efficient and simpler.

SUMMARY

The Applicants have discovered a catalytic system that allows the preparation of telechelic polymers via an efficient and simple process. The catalytic system has the distinctive feature of comprising a rare-earth metallocene and a co-catalyst which has two magnesium-carbon bonds involving different magnesium atoms.

Thus, a first subject of the invention is a catalytic system based at least:

-   -   on a metallocene of formula (Ia) or (Ib),     -   on an organomagnesium reagent of formula (II) as co-catalyst,

{P(Cp¹)(Cp²)Y}  (Ia)

Cp³Cp⁴Y  (Ib)

-   -   Y denoting a group including a rare-earth metal atom,     -   Cp¹, Cp², Cp³ and Cp⁴, which are identical or different, being         chosen from the group consisting of fluorenyl groups,         cyclopentadienyl groups and indenyl groups, the groups being         substituted or unsubstituted,     -   P being a group bridging the two groups Cp¹ and Cp² and         comprising a silicon or carbon atom,

X—Mg—R^(A)—Mg—X  (II)

-   -   R^(A) being a divalent aliphatic hydrocarbon-based chain,         interrupted or not with one or more oxygen or sulfur atoms or         with one or more arylene groups,     -   X being a halogen atom.

A second subject of the invention is a process for preparing a first telechelic polymer, which comprises a step of polymerization of a monomer M in the presence of a catalytic system in accordance with the invention, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof. The first telechelic polymer has the particular feature of bearing at each of its ends a terminal group having a reactive carbon-magnesium bond.

A third subject of the invention is a process for preparing a second telechelic polymer, which comprises a step of polymerization of a monomer M in the presence of a catalytic system in accordance with the invention, this polymerization step being followed by a step of functionalization with a modifying agent, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof. The second telechelic polymer has the particular feature of bearing a functional group at each of its ends.

The invention also relates to a telechelic polymer of formula X—Mg-poly-R^(A)-poly-Mg—X, R^(A) and X being defined as previously, the term “poly” in the formula denoting a polymer chain of a 1,3-diene, ethylene, an α-monoolefin or mixtures thereof. The telechelic polymer in accordance with the invention may be obtained via a process in accordance with the invention, which is the second subject of the invention.

The invention also relates to a process for preparing a polymer, which comprises a step of polymerization of a monomer M in the presence of a catalytic system in accordance with the invention and a termination reaction with a protic compound, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Any interval of values denoted by the expression “between a and b” represents the range of values greater than “a” and less than “b” (that is to say limits a and b excluded), whereas any interval of values denoted by the expression “from a to b” means the range of values extending from “a” up to “b” (that is to say including the strict limits a and b).

Unless otherwise indicated, the contents of the units resulting from the insertion of a monomer into a polymer are expressed as a molar percentage relative to the total monomer units that constitute the polymer.

The compounds mentioned in the description may be of fossil origin or may be biobased. In the latter case, they may be partially or totally derived from biomass or may be obtained from renewable starting materials derived from biomass. Similarly, the compounds mentioned may also be derived from the recycling of already-used materials, i.e. they may be partly or totally derived from a recycling process, or obtained from raw materials which are themselves derived from a recycling process.

The term “based on” used to define the constituents of the catalytic system means the mixture of these constituents, or the product of the reaction of a portion or all of these constituents with each other.

In the present patent application, the term “metallocene” means an organometallic complex, the metal of which, in the case in point the rare-earth metal atom, is bonded to two groups Cp³ and Cp⁴ or to a ligand molecule consisting of two groups Cp¹ and Cp² connected together by a bridge P. These groups Cp¹, Cp², Cp³ and Cp⁴, which are identical or different, are chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, these groups possibly being substituted or unsubstituted. It is recalled that rare-earth elements are metals and denote the elements scandium, yttrium and the lanthanides, the atomic number of which ranges from 57 to 71.

According to a first variant of the invention, the metallocene used as base constituent in the catalytic system in accordance with the invention corresponds to formula (Ia)

{P(Cp¹)(Cp²)Y}  (Ia)

-   -   in which     -   Y denotes a group including a rare-earth metal atom,     -   Cp¹ and Cp², which are identical or different, are chosen from         the group consisting of fluorenyl groups, cyclopentadienyl         groups and indenyl groups, the groups being substituted or         unsubstituted,     -   P is a group bridging the two groups Cp¹ and Cp² and comprising         a silicon or carbon atom.

According to a second variant of the invention, the metallocene used as base constituent in the catalytic system in accordance with the invention corresponds to formula (Ib)

Cp³Cp⁴Y  (Ib)

-   -   in which     -   Y denotes a group including a rare-earth metal atom,     -   Cp³ and Cp⁴, which are identical or different, are chosen from         the group consisting of fluorenyl groups, cyclopentadienyl         groups and indenyl groups, the groups being substituted or         unsubstituted.

As substituted cyclopentadienyl, fluorenyl and indenyl groups, mention may be made of those substituted with alkyl radicals containing from 1 to 6 carbon atoms or with aryl radicals containing from 6 to 12 carbon atoms or else with trialkylsilyl radicals, such as SiMe₃. The choice of the radicals is also guided by the accessibility to the corresponding molecules, which are the substituted cyclopentadienes, fluorenes and indenes, since said molecules are commercially available or can be readily synthesized.

As substituted fluorenyl groups, mention may be made of those substituted in position 2, 7, 3 or 6, particularly 2,7-di(tert-butyl)fluorenyl and 3,6-di(tert-butyl)fluorenyl. The 2, 3, 6 and 7 positions respectively denote the position of the carbon atoms of the rings as represented in the diagram below, the 9 position corresponding to the carbon atom to which the bridge P is attached.

As substituted cyclopentadienyl groups, mention may be made of those substituted in the 2 (or 5) position and also in the 3 (or 4) position, particularly those substituted in the 2 position, more particularly the tetramethylcyclopentadienyl group. Position 2 (or 5) denotes the position of the carbon atom which is adjacent to the carbon atom to which the bridge P is attached, as is represented in the diagram below.

As substituted indenyl groups, mention may be made particularly of those substituted in the 2 position, more particularly 2-methylindenyl or 2-phenylindenyl. Position 2 denotes the position of the carbon atom which is adjacent to the carbon atom to which the bridge P is attached, as is represented in the diagram below.

Preferably, the metallocene is of formula (Ia).

According to a preferential embodiment of the invention, Cp¹ and Cp² are identical and are chosen from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula C₁₃H₈. The catalytic system according to this preferential embodiment has the distinguishing feature of resulting in copolymers of butadiene and ethylene which comprise, in addition to the ethylene monomer units and the butadiene units of the cyclic units, 1,2-cyclohexane units having the following formula:

The cyclic units result from a particular insertion of ethylene and 1,3-butadiene monomers into the polymer chain, in addition to the conventional ethylene and 1,3-butadiene units, respectively —(CH₂—CH₂)—, —(CH₂—CH═CH—CH₂)— and —(CH₂—CH(C═CH₂))—. The mechanism for obtaining such a microstructure is described, for example, in Macromolecules 2009, 42, 3774-3779.

Advantageously, Cp¹ and Cp² are identical and each represent an unsubstituted fluorenyl group of formula C₁₃H₈, represented by the symbol Flu.

According to a preferential embodiment of the invention, the symbol Y represents the group Met-G, with Met denoting the rare-earth metal and G denoting a group comprising the borohydride BH₄ unit or denoting a halogen atom chosen from the group consisting of chlorine, fluorine, bromine and iodine. Advantageously, G denotes a chlorine atom or the group of formula (III):

(BH₄)_((1+y))-L_(y)-N_(x)  (III)

-   -   in which     -   L represents an alkali metal chosen from the group consisting of         lithium, sodium and potassium,     -   N represents a molecule of an ether,     -   x, which may or may not be an integer, is greater than or equal         to 0,     -   y, which is an integer, is greater than or equal to 0.

Very advantageously, G denotes the group of formula (III).

Any ether which has the ability to complex the alkali metal, notably diethyl ether and tetrahydrofuran, is suitable as ether.

According to any one of the embodiments of the invention, the metal of the metallocene that is useful for the purposes of invention, in the case in point the rare-earth metal, is preferably a lanthanide, the atomic number of which ranges from 57 to 71, more preferentially neodymium, Nd.

The bridge P connecting the groups Cp¹ and Cp² preferably corresponds to the formula ZR¹R², in which Z represents a silicon or carbon atom and R¹ and R², which are identical or different, each represent an alkyl group comprising from 1 to 20 carbon atoms, preferably a methyl. In the formula ZR¹R², Z advantageously represents a silicon atom, Si.

The metallocene that is useful for the synthesis of the catalytic system may be in the form of a crystalline or non-crystalline powder, or else in the form of single crystals. The metallocene may be in a monomer or dimer form, these forms depending on the method of preparation of the metallocene, as is described, for example, in patent application WO 2007/054224 or WO 2007/054223. The metallocene may be prepared conventionally by a process analogous to that described in patent application WO 2007/054224 or WO 2007/054223, notably by reaction, under inert and anhydrous conditions, of the salt of an alkali metal of the ligand with a rare-earth metal borohydride in a suitable solvent, such as an ether, for instance diethyl ether or tetrahydrofuran, or any other solvent known to those skilled in the art. After reaction, the metallocene is separated from the reaction by-products via techniques known to those skilled in the art, such as filtration or precipitation from a second solvent. The metallocene is finally dried and isolated in solid form.

According to a particularly preferential embodiment, the metallocene is of formula (III-1), (III-2), (III-3), (III-4) or (III-5):

[Me₂Si(Flu)₂Nd(μ-BH₄)₂Li(THF)]  (III-1)

[{Me₂SiFlu₂Nd(μ-BH₄)₂Li(THF)}₂]  (III-2)

[Me₂SiFlu₂Nd(μ-BH₄)(THF)]  (III-3)

[{Me₂SiFlu₂Nd(μ-BH₄)(THF)}₂]  (III-4)

[Me₂SiFlu₂Nd(μ-BH₄)]  (III-5)

in which Flu represents the C₁₃H₈ group.

Another basic component of the catalytic system in accordance with the invention is the co-catalyst, an organomagnesium reagent of formula (II) in which R^(A) is a divalent aliphatic hydrocarbon-based chain, interrupted or not with one or more oxygen or sulfur atoms or with one or more arylene groups and X is a halogen atom, preferably a chlorine or bromine atom.

X—Mg—R^(A)—Mg—X  (II)

The co-catalyst of formula (II) has the particular feature of including two magnesium-carbon bonds involving different magnesium atoms. In formula (II), each magnesium atom thus shares a first bond with a halogen atom and a second bond with a carbon atom of R^(A).

R^(A) is a divalent aliphatic hydrocarbon-based chain which may contain within its chain one or more heteroatoms chosen from oxygen and sulfur or one or more arylene groups. Preferably, R^(A) is a branched or linear alkanediyl, cycloalkanediyl or xylenediyl radical. More preferentially, R^(A) is an alkanediyl. Preferably, R^(A) contains 3 to 10 carbon atoms, in particular 3 to 8 carbon atoms. Even more preferentially, R^(A) is an alkanediyl containing 3 to 10 carbon atoms. Advantageously, R^(A) is an alkanediyl containing 3 to 8 carbon atoms. Very advantageously, R^(A) is a linear alkanediyl. 1,3-propanediyl, 1,4-butanediyl, 1,5-pentanediyl, 1,6-hexanediyl, 1,7-heptanediyl and 1,8-octanediyl are most particularly suitable as groups R^(A).

The compounds of formula (II) are well known as Grignard reagents. However, they are not known to be used as co-catalysts in a catalytic system for use in the preparation of polyolefins. Grignard reagents of formula (II) are described, for example, in the book “Advanced Organic Chemistry” by J. March, 4th Edition, 1992, pages 622-623 or in the book “Handbook of Grignard Reagents”, Edition Gary S. Silverman, Philip E. Rakita, 1996, pages 502-503. They may be synthesized by placing magnesium metal in contact with a dihalogen compound of formula X—R^(A)—X, R^(A) being as defined according to the invention. For their synthesis, reference may be made, for example, to the collection of volumes of “Organic Synthesis”.

Like any organomagnesium compound, the organomagnesium reagent of formula X—Mg—R^(A)—Mg—X that is useful for the purposes of the invention may be in the form of a monomeric species (X—Mg—R^(A)—Mg—X)₁ or in the form of a polymeric species (X—Mg—R^(A)—Mg—X)_(p), where p is an integer greater than 1, notably dimer (X—Mg—R^(A)—Mg—X)₂. Moreover, whether it is in the form of a monomer or polymer species, it may also be in the form of a species coordinated to one or more molecules of a solvent, preferably of an ether such as diethyl ether, tetrahydrofuran or methyltetrahydrofuran.

The catalytic system in accordance with the invention may be prepared conventionally via a process analogous to that described in patent application WO 2007/054224 or WO 2007/054223. For example, the organomagnesium reagent X—Mg—R^(A)—Mg—X that is useful for the purposes of the invention and the metallocene are reacted in a hydrocarbon-based solvent typically at a temperature ranging from 20 to 80° C. for a period of between 5 and 60 minutes. The amounts of co-catalyst and of metallocene reacted are such that the ratio between the number of moles of Mg of the co-catalyst and the number of moles of rare-earth metal of the metallocene is preferably from 1 to 200 and more preferentially from 1 to less than 20. The range of values extending from 1 to less than 20 is notably more favourable for obtaining polymers of high molar masses. The catalytic system is generally prepared in an aliphatic hydrocarbon-based solvent such as methylcyclohexane, or an aromatic hydrocarbon-based solvent such as toluene. Generally, after its synthesis, the catalytic system is used as is in the process for the synthesis of the polymer in accordance with the invention.

Alternatively, the catalytic system in accordance with the invention may be prepared via a process analogous to that described in patent application WO 2017/093654 A1 or in patent application WO 2018/020122 A1. According to this alternative, the catalytic system also contains a preformation monomer chosen from a conjugated diene, ethylene or a mixture of ethylene and a conjugated diene, in which case the catalytic system is based at least on the metallocene, the organomagnesium reagent X—Mg—R^(A)—Mg—X that is useful for the purposes of the invention and the preformation monomer. For example, the organomagnesium reagent and the metallocene are reacted in a hydrocarbon-based solvent typically at a temperature of from 20° C. to 80° C. for 10 to 20 minutes to obtain a first reaction product, and the preformation monomer, chosen from a conjugated diene, ethylene or a mixture of ethylene and a conjugated diene, is then reacted with this first reaction product at a temperature ranging from 40° C. to 90° C. for 1 hour to 12 hours. The conjugated diene, as preformation monomer, is preferably a 1,3-diene such as 1,3-butadiene, isoprene or a 1,3-diene of formula CH₂═CR—CH═CH₂, the symbol R representing a hydrocarbon chain containing 3 to 20 carbon atoms, in particular myrcene or β-farnesene. The catalytic system thus obtained may be used directly in the process in accordance with the invention or may be stored under an inert atmosphere, notably at a temperature ranging from −20° C. to room temperature (23° C.), before being used in the synthesis of polymers.

Like any synthesis performed in the presence of an organometallic compound, the synthesis of the metallocene, the synthesis of the organomagnesium reagent and the synthesis of the catalytic system take place under anhydrous conditions under an inert atmosphere. Typically, the reactions are performed starting with anhydrous solvents and compounds under anhydrous nitrogen or argon.

The catalytic system may be in the form of a solution when it is in the presence of a hydrocarbon-based solvent. The hydrocarbon-based solvent may be aliphatic, such as methylcyclohexane, or aromatic, such as toluene. The hydrocarbon-based solvent is preferably aliphatic, more preferentially methylcyclohexane. Generally, the catalytic system is stored in the form of a solution in the hydrocarbon-based solvent before being used in polymerization. This may then be referred to as a catalytic solution which comprises the catalytic system and the hydrocarbon-based solvent. According to any of the embodiments of the invention, the catalytic system preferably comprises a hydrocarbon-based solvent. When the catalytic system is in solution, its concentration is defined by the content of metallocene metal in the solution. The concentration of metallocene metal has a value preferentially ranging from 0.0001 to 0.2 mol/L, more preferentially from 0.001 to 0.03 mol/L.

The catalytic system according to the invention is intended to be used in processes for the synthesis of polymers, notably elastomers, which may be used in rubber compositions, for example for tyres.

A first process allows the preparation of telechelic polymers which have the particular feature of having a carbon-magnesium bond at each of their ends. The first process comprises a polymerization step in the presence of a catalytic system in accordance with the invention.

A second process allows the preparation of telechelic polymers which have the particular feature of having a functional group at each of their ends. It comprises a polymerization step followed by a step of functionalization with a modifying agent. The polymerization step is identical to that of the first process. The modifying agent is typically a compound known to react with a compound containing a carbon-magnesium bond. Particularly suitable modifying agents are dihalogens and ketones. The functional groups at the ends of the polymer are advantageously identical. The modifying agent is typically added to the polymerization medium. The functionalized polymer can be recovered according to conventional techniques known to those skilled in the art, for instance by precipitation, by evaporation of the solvent under reduced pressure or by steam stripping.

A third process comprises a polymerization step and a termination reaction with a protic compound. The polymerization step is identical to that of the first process and the second process. The protic compound allows the polymerization to be stopped by a termination reaction without adding functions to the polymer ends. The protic compound is, for example, an alcohol such as methanol, ethanol, isopropanol or water. It may be added to the polymerization medium. Alternatively, the polymerization medium may be poured into the protic compound such as methanol or into a solution containing the protic compound, for example a toluene solution containing methanol.

According to a particular embodiment of the third process, the protic compound is a compound which allows the labelling of the polymer ends with an isotope of the hydrogen atom such as deuterium. Suitable labelled protic compounds are deuterated water and alcohols with a hydroxyl group OD. The polymer formed can be recovered according to conventional techniques known to those skilled in the art, for instance by precipitation, by evaporation of the solvent under reduced pressure or by steam stripping.

The polymerization reaction common to the three processes in accordance with the invention is a polymerization reaction of a monomer M chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof. The term “α-monoolefin” means an α-olefin which contains a single carbon-carbon double bond, the double bonds in aromatic compounds not being taken into account. For example, styrene is considered an α-monoolefin. Preferably, the monomer M is ethylene or a mixture of a 1,3-diene and ethylene or a mixture of a 1,3-diene, ethylene and an α-monoolefin such as styrene, the 1,3-diene advantageously being 1,3-butadiene, isoprene or mixtures thereof.

The polymerization is preferably performed in solution, continuously or batchwise. The polymerization solvent may be an aromatic or aliphatic hydrocarbon-based solvent. Examples of polymerization solvents that may be mentioned include toluene and methylcyclohexane. The monomer M may be introduced into the reactor containing the polymerization solvent and the catalytic system or, conversely, the catalytic system may be introduced into the reactor containing the polymerization solvent and the monomer M. The monomer M and the catalytic system may be introduced simultaneously into the reactor containing the polymerization solvent, notably in the case of a continuous polymerization. The polymerization is typically performed under anhydrous conditions and in the absence of oxygen, in the optional presence of an inert gas. The polymerization temperature generally varies within a range extending from 25 to 120° C., preferentially from 30 to 100° C. It is adjusted according to the monomer to be polymerized. Preferably, the copolymerization is performed at a constant pressure of ethylene.

During the polymerization of ethylene and of 1,3-dienes in a polymerization reactor, ethylene and 1,3-dienes may be added continuously to the polymerization reactor, in which case the polymerization reactor is a fed reactor. This embodiment is most particularly suitable for the synthesis of a statistical copolymer.

Thus, via simple processes comprising a polymerization reaction and a reaction with a modifying agent or a labelled protic compound, polymers whose two ends bear identical functional groups or which are labelled with an isotope may be synthesized.

Labelled polymers and end-functional polymers are obtained from telechelic polymers which contain a carbon-magnesium bond at the ends and which may be obtained via the first process. Telechelic polymers with a carbon-magnesium bond at the ends are therefore capable of giving rise, on the one hand, to the formation of polymers whose two ends are marked with an isotope of the hydrogen atom and, on the other hand, to the formation of polymers whose two ends bear identical functional groups.

Telechelic polymers containing a carbon-magnesium bond at the ends may be represented by formula (IV) in which R^(A) and X are defined as previously, including according to the preferential embodiments, the term “poly” denotes a polymer chain of a 1,3-diene, ethylene, an α-monoolefin or mixtures thereof.

X—Mg-poly-R^(A)-poly-Mg—X  (IV)

Preferably, the polymer chain denoted by the term “poly” is a polymer chain of ethylene or a polymer chain of a 1,3-diene and ethylene or a polymer chain of a 1,3-diene, ethylene and an α-monoolefin such as styrene. The 1,3-diene is a 1,3-diene or a mixture of 1,3-dienes. 1,3-dienes that are most particularly suitable for use are 1,3-dienes containing 4 to 24 carbon atoms, such as 1,3-butadiene, isoprene and mixtures thereof. According to a particular embodiment, the polymer chain denoted by the name “poly” contains ethylene units, 1,3-butadiene units and cyclic units, 1,2-cyclohexane units of the following formula.

According to the particular embodiment in which the polymer chain denoted by the name “poly” contains 1,2-cyclohexane units, it preferentially contains not more than 15 mol % thereof. The cyclic units result from a particular insertion of ethylene and 1,3-butadiene monomers into the polymer chain, in addition to the conventional ethylene and 1,3-butadiene units, —(CH₂—CH₂)—, —(CH₂—CH═CH—CH₂)— and —(CH₂—CH(C═CH₂))—, respectively. The mechanism for obtaining such a microstructure is described, for example, in Macromolecules 2009, 42, 3774-3779.

According to any one of the embodiments of the invention, the polymer chain denoted by the name “poly” preferentially contains more than 50 mol % ethylene units.

According to a particularly preferential embodiment of the invention, the polymer chain denoted by the name “poly” is a statistical polymer chain of a 1,3-diene and ethylene or a statistical polymer chain of a 1,3-diene, ethylene and an α-monoolefin such as styrene.

In summary, the invention is advantageously performed according to any one of the following embodiments 1 to 35:

Embodiment 1: Catalytic system based at least:

-   -   on a metallocene of formula (Ia) or (Ib), preferably (Ia),     -   on an organomagnesium reagent as co-catalyst,

{P(Cp¹)(Cp²)Y}  (Ia)

Cp³Cp⁴Y  (Ib)

-   -   Y denoting a group including a rare-earth metal atom,     -   Cp¹, Cp², Cp³ and Cp⁴, which are identical or different, being         chosen from the group consisting of fluorenyl groups,         cyclopentadienyl groups and indenyl groups, the groups being         substituted or unsubstituted,     -   P being a group bridging the two groups Cp¹ and Cp² and         comprising a silicon or carbon atom,     -   the organomagnesium reagent being a compound of formula (II)

X—Mg—R^(A)—Mg—X  (II)

-   -   R^(A) being a divalent aliphatic hydrocarbon-based chain,         interrupted or not with one or more oxygen or sulfur atoms or         with one or more arylene groups,     -   X being a halogen atom.

Embodiment 2: Catalytic system according to embodiment 1, in which X is a chlorine or bromine atom.

Embodiment 3: Catalytic system according to either of embodiments 1 and 2, in which the metallocene is of formula (Ia).

Embodiment 4: Catalytic system according to any one of embodiments 1 to 3, in which Cp¹ and Cp² are identical and are chosen from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula C₁₃H₈.

Embodiment 5: Catalytic system according to any one of embodiments 1 to 4, in which Cp¹ and Cp² each represent an unsubstituted fluorenyl group of formula C₁₃H₈.

Embodiment 6: Catalytic system according to any one of embodiments 1 to 5, in which the symbol Y represents the group Met-G, with Met denoting the rare-earth metal atom and G denoting a group comprising the borohydride BH₄ unit or denoting a halogen atom chosen from the group consisting of chlorine, fluorine, bromine and iodine.

Embodiment 7: Catalytic system according to embodiment 6, in which G denotes a chlorine atom or the group of formula (III)

(BH₄)_((1+y))-L_(y)-N_(x)  (III)

-   -   in which     -   L represents an alkali metal chosen from the group consisting of         lithium, sodium and potassium,     -   N represents a molecule of an ether, preferably diethyl ether or         tetrahydrofuran,     -   x, which may or may not be an integer, is greater than or equal         to 0,     -   y, which is an integer, is greater than or equal to 0.

Embodiment 8: Catalytic system according to embodiment 7, in which G denotes the group of formula (III).

Embodiment 9: Catalytic system according to any one of embodiments 1 to 8, in which the rare-earth metal is a lanthanide, the atomic number of which ranges from 57 to 71.

Embodiment 10: Catalytic system according to any one of embodiments 1 to 9, in which the rare-earth metal is neodymium.

Embodiment 11: Catalytic system according to any one of embodiments 1 to 10, in which the bridge P corresponds to the formula ZR¹R², Z representing a silicon or carbon atom, R¹ and R², which are identical or different, each representing an alkyl group comprising from 1 to 20 carbon atoms.

Embodiment 12: Catalytic system according to embodiment 11 in which R¹ and R² each represent a methyl.

Embodiment 13: Catalytic system according to either one of embodiments 11 and 12, in which Z represents a silicon atom.

Embodiment 14: Catalytic system according to any one of embodiments 1 to 13, in which the metallocene is of formula (III-1), (III-2), (III-3), (III-4) or (III-5):

[Me₂Si(Flu)₂Nd(μ-BH₄)₂Li(THF)]  (III-1)

[{Me₂SiFlu₂Nd(μ-BH₄)₂Li(THF)}₂]  (III-2)

[Me₂SiFlu₂Nd(μ-BH₄)(THF)]  (III-3)

[{Me₂SiFlu₂Nd(μ-BH₄)(THF)}₂]  (III-4)

[Me₂SiFlu₂Nd(μ-BH₄)]  (III-5)

-   -   Flu representing the C₁₃H₈ group.

Embodiment 15: Catalytic system according to any one of embodiments 1 to 14, in which R^(A) is a branched or linear alkanediyl, cycloalkanediyl or xylenediyl radical.

Embodiment 16: Catalytic system according to any one of embodiments 1 to 15, in which R^(A) contains from 3 to 10 carbon atoms.

Embodiment 17: Catalytic system according to any one of embodiments 1 to 16, in which R^(A) contains from 3 to 8 carbon atoms.

Embodiment 18: Catalytic system according to any one of embodiments 1 to 17, in which R^(A) is a linear alkanediyl.

Embodiment 19: Catalytic system according to any one of embodiments 1 to 18, in which the ratio between the number of moles of Mg of the co-catalyst and the number of moles of rare-earth metal of the metallocene ranges from 1 to 200.

Embodiment 20: Catalytic system according to any one of embodiments 1 to 18, in which the ratio between the number of moles of Mg of the co-catalyst and the number of moles of rare-earth metal of the metallocene ranges from 1 to less than 20.

Embodiment 21: Process for preparing a first telechelic polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in any one of embodiments 1 to 20, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.

Embodiment 22: Process for preparing a second telechelic polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in any one of embodiments 1 to 20, this polymerization step being followed by a step of functionalization with a modifying agent, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.

Embodiment 23: Process for preparing a polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in any one of embodiments 1 to 20 and a termination reaction with a protic compound, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.

Embodiment 24: Preparation process according to any one of embodiments 21 to 23, in which the monomer M is ethylene or a mixture of a 1,3-diene and ethylene or a mixture of a 1,3-diene, ethylene and an α-monoolefin.

Embodiment 25: Preparation process according to embodiment 24, in which the 1,3-diene is 1,3-butadiene, isoprene or mixtures thereof.

Embodiment 26: Telechelic polymer of formula (IV)

X—Mg-poly-R^(A)-poly-Mg—X  (IV)

-   -   in which R^(A) is a divalent aliphatic hydrocarbon-based chain,         interrupted or not with one or more oxygen or sulfur atoms or         with one or more arylene groups, X is a halogen atom, the term         “poly” denotes a polymer chain of a 1,3-diene, ethylene, an         α-monoolefin or mixtures thereof.

Embodiment 27: Telechelic polymer according to embodiment 26, in which the polymer chain denoted by the name “poly” is a polymer chain of ethylene or a polymer chain of a 1,3-diene and ethylene or a polymer chain of a 1,3-diene, ethylene and an α-monoolefin.

Embodiment 28: Telechelic polymer according to either of embodiments 26 and 27, in which the polymer chain denoted by the name “poly” denotes a polymer chain which contains ethylene units, 1,3-butadiene units and cyclic units, 1,2-cyclohexane units of the following formula.

Embodiment 29: Telechelic polymer according to any one of embodiments 26 to 28, in which the polymer chain denoted by the name “poly” denotes a polymer chain containing more than 50 mol % of ethylene units.

Embodiment 30: Telechelic polymer according to any one of embodiments 26 to 29, in which the polymer chain denoted by the name “poly” denotes a statistical polymer chain of a 1,3-diene, ethylene and an α-monoolefin.

Embodiment 31: Telechelic polymer according to any one of embodiments 26 to 30, in which R^(A) is an alkanediyl, branched or linear, a cycloalkanediyl or a xylenediyl radical.

Embodiment 32: Telechelic polymer according to any one of embodiments 26 to 31, in which R^(A) contains from 3 to 10 carbon atoms.

Embodiment 33: Telechelic polymer according to any one of embodiments 26 to 32, in which R^(A) contains from 3 to 8 carbon atoms.

Embodiment 34: Telechelic polymer according to any one of embodiments 26 to 33, in which R^(A) represents a linear alkanediyl.

Embodiment 35: Telechelic polymer according to any one of embodiments 26 to 34, in which X is a chlorine or bromine atom.

The abovementioned features of the present invention, and also others, will be understood more clearly on reading the following description of implementation examples of the invention, which are given as non-limiting illustrations.

EXAMPLES Example 1: Preparation of a Co-Catalyst in Accordance with the Invention, 1,5-di(magnesium bromide)pentanediyl (DBMP)

9.72 g of magnesium (400 mmol, 10 equivalents), 80 mL of MeTHF (of which 64 mL in the dropping funnel), 60 mg of diiodine (0.23 mmol, 0.006 equivalent) and 5.45 mL of 1,5-dibromopentane (40 mmol, 1 equivalent) were used in the synthesis. The glassware used consisted of a 200 mL flask and a 100 mL dropping funnel. Once the synthesis of the Grignard reagent was complete, the solution is transferred through the filter cannula into a second inertized 200 mL flask. This solution is concentrated under vacuum and then diluted in 55 mL of toluene. The concentration of pentanediyl group is estimated at 0.45 mol L⁻¹. This oil is immiscible in methylcyclohexane.

Aliquot of the concentrated oil: ¹H NMR (toluene-D₈-500 MHz-298 K) δ: ppm=2.21 (quint, J=7.2 Hz, “b”), 1.88 (quint, J=7.0 Hz, “c”), 0.11 (t, J=7.4 Hz, “a”); quint for quintet.

Example 2: Synthesis of 2-mesitylmagnesium bromide

4.15 g (170 mmol, 3.4 equivalents) of magnesium are inertized in a 250 mL flask fitted with a magnetized olive and mounted with a 10 mL dropping funnel. A diiodine bead (10 mg) is added to the magnesium. 47.5 mL of MeTHF are placed in the flask with stirring and 2.5 mL are placed in the dropping funnel. 7.65 mL of degassed 2-bromomesitylene (50 mmol, 1 equivalent) dried over activated molecular sieves are placed in the dropping funnel. The flask is heated to 60° C. and the 2-bromomesitylene is added dropwise to the magnesium over 1 hour. Stirring is continued for 3 h at 60° C. and then for 12 h at 20° C.

Aliquot of the concentrated oil in a Young's tube: ¹H NMR (C₆D₆-400 MHz-298 K) δ: ppm=7.01 (s, “a”), 2.74 (s, “b”), 2.36 (s, “c”)

High resolution NMR spectroscopy of organometallic compounds was performed on a Bruker 400 Avance III spectrometer operating at 400 MHz equipped with a 5 mm BBFO probe or on a Bruker 500 Avance III spectrometer operating at 500 MHz equipped with a 5 mm BBFO probe. Acquisitions were made at 298 K or 340 K in deuterated benzene (C₆D₆). The samples were analysed at a concentration of 5% by mass. The chemical shifts are given in ppm, relative to the C₆D₆ proton signal set at 7.16 ppm and the carbon signal set at 128.06 ppm. The structure of the magnesium compounds is characterized by 1D ¹H, ¹H-¹³C HSQC ((Heteronuclear Single Quantum Coherence), ¹H-¹³C HMBC (Heteronuclear Multiple-Bond Correlation) nuclear magnetic resonance NMR and NOESY. The magnesium compound is analysed with its synthesis solvent and deuterated benzene (C₆D₆) is added to the solution to obtain the NMR “lock”.

Synthesis of Telechelic and Functional Polymers:

Ethylene homopolymers and ethylene-butadiene copolymers were prepared from the complex {(Me₂Si(C₁₃H₈)₂)Nd(—BH₄)[(—BH₄)Li(THF)]}₂ and the co-catalyst 1,5-di(magnesium bromide)pentanediyl (DBMP) prepared according to the procedure described above in Example 1. The polymers were characterized using the methods described hereinbelow.

High temperature size exclusion chromatography (HT-SEC). The high temperature size exclusion chromatography (HT-SEC) analyses were performed with a Viscotek machine (Malvern Instruments) equipped with three columns (PLgel Olexis 300 mm×7 mm I. D. from Agilent Technologies) and three detectors (differential refractometer and viscometer, and light scattering). 200 μL of a solution of the sample at a concentration of 3 mg mL⁻¹ were eluted in 1,2,4-trichlorobenzene using a flow rate of 1 mL min⁻¹ at 150° C. The mobile phase was stabilized with 2,6-di(tert-butyl)-4-methylphenol (400 mg L⁻¹). OmniSEC software was used for data acquisition and analysis. The number-average molar mass (M_(n)) and mass-average molar mass (MW) of the synthesized polyethylenes, and their dispersity (Ð=M_(w)/M_(n)), were calculated using a calibration curve obtained from standard polyethylenes (peak molar mass M_(p): 338, 507, 770, 1890, 17 000, 27 300, 43 400, 53 100, 65 700, 78 400 g·mol⁻¹) from Polymer Standard Service (Mainz). The number-average molar mass (Mn) and mass-average molar mass (Mw) of the synthesized ethylene-butadiene copolymers, and their polydispersity index (D=Mw/M_(n)), were calculated using a universal calibration curve calibrated from standard polystyrenes (M_(p): 672 to 12 000 000 g mol⁻¹) from Polymer Standard Service (Mainz) using refractometric and viscometric detectors.

THF size exclusion chromatography (THF-SEC). The size exclusion chromatography analyses were performed with a Viscotek machine (Malvern Instruments). This machine is equipped with three columns (SDVB, 5 μm, 300×7.5 mm from Polymer Standard Service), a guard column and three detectors (differential refractometer and viscometer, and light scattering). 3 mL of a solution of the sample with a concentration of 3 mg mL⁻¹ in THF were filtered through a 0.45 μm PTFE membrane. 100 μL of this solution were eluted in THF using a flow rate of 1 mL min⁻¹ at a temperature of 35° C. OmniSEC software was used for data acquisition and analysis. The number-average molar mass (Mn) and mass-average molar mass (Mw) of the synthesized ethylene-butadiene copolymers, and their polydispersity index or dispersity (Ð=Mw/Mn), were calculated using a universal calibration curve obtained from standard polystyrenes (M_(p): 1306 to 2 520 000 g mol⁻¹) from Polymer Standard Service (Mainz).

Nuclear magnetic resonance (NMR). High resolution NMR spectroscopy of the polymers was performed on a Bruker 400 Avance III spectrometer operating at 400 MHz equipped with a 5 mm BBFO probe for the proton and on a Bruker 400 Avance II spectrometer operating at 400 MHz equipped with a 10 mm PSEX ¹³C probe for the carbon. Acquisitions were made at 363 K. A mixture of tetrachloroethylene (TCE) and deuterated benzene (C₆D₆) (2/1 v/v) was used as solvent. The samples were analysed at a concentration of 1% by mass for proton and 5% by mass for carbon. The chemical shifts are given in ppm, relative to the deuterated benzene proton signal set at 7.16 ppm and the TCE carbon signal set at 120.65 ppm. The sequence used to acquire a ¹³C spectrum of a polymer is: “Power gate decoupling” (NOE proton-decoupled spectrum) with a pulse angle of 70°, DT=64 K and a delay between pulses of 4.5 s. The number of acquisitions is set at 5120.

Synthesis of Telechelic and Labelled Polyethylenes:

Example PE1

200 mL of toluene distilled over sodium/benzophenone are placed in an inertized 250 mL flask fitted with a magnetized olive. 3.0 mL (1.35 mmol) of 1,5-di(magnesium bromide)pentanediyl prepared according to Example 1 (0.45 mol L⁻¹ in toluene) are added to the flask with stirring. 10.0 mg (15.6 μmol as neodymium) of {(Me₂Si(C₁₃H₈)₂)Nd(—BH₄)[(—BH₄)Li(THF)]}₂ are then added to the flask.

The catalytic solution is cannulated, i.e. transferred by way of a cannula, into a 250 mL reactor under an inert atmosphere. The argon excess pressure in the reactor is reduced to 0.5 bar and the reactor is then pressurized to 4 bar and the temperature is simultaneously brought to 70° C. The pressure is kept constant in the reactor by means of a tank containing ethylene.

When the desired amount of ethylene has been consumed, in this case after 49 min, the reactor is degassed and the temperature is reduced to 20° C. 40% of the polymer solution is cannulated out of the reactor and the polymer contained in this 40% is then precipitated from methanol with stirring. 2.0 mL (44 mmol, 15 equivalents/Mg) of deuterated methanol diluted in 5 mL of toluene are added to the polymer solution remaining in the reactor. After 1 h of stirring, the polymer solution is poured onto methanol with stirring to precipitate the polymer.

Each polymer was filtered off, washed with methanol and then dried. 1.14 g of PE1M polymer: D-(CH₂—CH₂)_(n)—(CH₂)₅—(CH₂—CH₂)_(n)-D and 0.70 g of PE1NF polymer: H—(CH₂—CH₂)_(n)—(CH₂)₅—(CH₂—CH₂)_(n)—H are recovered.

The proton NMR spectrum of the PE1M polymer (TCE/C₆D₆ 2/1 v/v, 400 MHz, 363 K) allows the observation of methylene in the α-position of deuterium at 6=0.83 (broad, —CH ₂D)).

The degree of labelling in the PE1M polymer is calculated by determining the content of unlabelled chains in the polymer. The content of unlabelled chains in PE1M is determined by normalizing the integrals of the (CH₂CH₂)_(n) signals of the two ¹³C NMR spectra to 100 and then dividing the integral of the CH₃ signals of the PE1M polymer by that of the CH₃ signals of the PE1NF polymer. Thus in PE1M, 11% of the polymer chain ends are unlabelled, and thus 89% of the polymer chain ends have been labelled with a deuterium atom.

The conditions for the polymerization of ethylene are given in Table 1. Table 1 also shows for each example the catalytic activity calculated over the entire polymerization time and expressed in Kg·mol⁻¹·h⁻¹. The characteristics of the synthesized polyethylenes are shown in Table 2. The HT-SEC method was used.

Synthesis of Telechelic and Functional Copolymers of Ethylene and 1,3-Butadiene:

Example EBR1

200 mL of toluene distilled over sodium/benzophenone are added to an inertized 250 mL flask fitted with a magnetized olive. 3.0 mL (1.35 mmol) of 1,5-di(magnesium bromide)pentanediyl prepared according to Example 1 (0.45 mol·L⁻¹ in toluene) are added to the flask with stirring. 32.0 mg (50 μmol neodymium) of {(Me₂Si(C₁₃H₈)₂)Nd(—BH₄)[(—BH₄)Li(THF)]}₂ are then added to the flask. A 250 mL reactor is pressurized with an 80/20 mole ratio ethylene/butadiene mixture.

The catalytic solution is cannulated into the 250 mL reactor under an inert atmosphere. The argon excess pressure in the reactor is reduced to 0.5 bar, the reactor is then pressurized to 4 bar with an 80/20 molar ethylene/butadiene mixture and the temperature is simultaneously brought to 70° C. The pressure is kept constant in the reactor by means of a tank containing an 80/20 molar ethylene/butadiene gas mixture.

When the desired amount of monomer has been consumed, in this case after 2 hours 55 minutes, the reactor is degassed and the temperature is reduced to 20° C. The polymer is then precipitated from methanol with stirring in the presence of 5 mg of stabilizer 2,2′-methylenebis(6-tert-butyl-4-methylphenol). The polymer is washed with methanol and dried. 11.0 g of polymer are recovered.

Example EBR2

310 mL of toluene purified on an activated alumina column (also known as a solvent fountain) are placed in a 750 mL Steinie bottle. After sparging with nitrogen for about 10 minutes, 300 mL of toluene are thus recovered. 46 mg (72 μmol of neodymium) of {(Me₂Si(C₁₃H₈)₂)Nd(—BH₄)[(—BH₄)Li(THF)]}₂ complex are weighed out in a 250 mL Steinie bottle in a glovebox. About 100 mL of the contents of the 750 mL bottle are transferred into the 250 mL bottle via a double-needle system. 2.3 mL of 1,5-di(magnesium bromide)pentanediyl (DMBP) prepared according to the same method as described in Example 1 (0.43 mol·L⁻¹ in toluene) are added to the 250 mL bottle.

A further 100 mL of the contents of the 750 mL bottle are added to an inertized 500 mL reactor with stirring (400 rpm) and heated to 77° C. The contents of the 250 mL bottle are then transferred into the reactor and the remaining contents of the 750 mL bottle (about 100 mL) complete the filling of the reactor. The reactor is degassed under vacuum until gas bubbles form and then pressurized to 3 bar with the ethylene/butadiene mixture at an 80/20 mole ratio.

When the desired amount of monomer has been consumed, the reactor is degassed. Functionalization is performed with two equivalents of 4,4′-bis(diethylamino)benzophenone (DEAB) relative to the total amount of magnesium, dissolved in toluene.

The medium is stirred for 1 h at 77° C. and then cooled and deactivated with ethanol. The polymer is dried under vacuum at 50° C. for 24 h and then weighed.

About 2 g of polymer are dissolved in 20 mL of methylcyclohexane, and the polymer is then precipitated from about 150 mL of acetone. The operation is repeated three times in succession to wash the polymer. The washed and dried polymer is recovered for analysis.

Example EBR3

200 mL of toluene from the solvent fountain are placed in an inertized 250 mL flask equipped with a magnetized olive. 2.3 mL (1.0 mmol) of 1,5-di(magnesium bromide)pentanediyl prepared according to Example 1 (0.43 mol L⁻¹ in toluene) are added to the flask with stirring. 32.0 mg (50 μmol as neodymium) of {(Me₂Si(C₁₃H₈)₂)Nd(—BH₄)[(—BH₄)Li(THF)]}₂ are then added to the flask.

The catalytic solution is cannulated into a 250 mL reactor under an inert atmosphere. The argon excess pressure in the reactor is reduced to 0.5 bar, and the reactor is then pressurized to 4 bar with an 80/20 molar ethylene/butadiene mixture and the temperature is simultaneously brought to 70° C. The pressure is kept constant in the reactor by means of a tank containing an 80/20 molar ethylene/butadiene gas mixture.

The reactor is degassed when 10 g of the target monomers are consumed, in this case after 175 min, and the temperature is reduced to 20° C.

To determine the microstructure and macrostructure of the telechelic polymer, the polymer solution is poured onto methanol with stirring to precipitate the polymer. The polymer is washed with methanol and then dried. 10.57 g of polymer are recovered.

Example EBR4

310 mL of toluene from a solvent fountain are added to a 750 mL Steinie bottle. After sparging with nitrogen for about 10 minutes, 300 mL of toluene are thus recovered. 46 mg (72 μmol of neodymium) of {(Me₂Si(C₁₃H₈)₂)Nd(—BH₄)[(—BH₄)Li(THF)]}₂ complex are weighed out in a 250 mL Steinie bottle in a glovebox. 1 mL of 2-mesitylmagnesium bromide prepared according to Example 2 (0.5 mol·L⁻¹ in toluene) is introduced into the 750 mL bottle. About 100 mL of the contents of the 750 mL bottle are transferred into the 250 mL bottle via a double-needle system. 2.3 mL of 1,5-di(magnesium bromide)pentanediyl (DMBP) prepared according to the same method as described in Example 1 (0.43 mol·L⁻¹ in toluene) are added to the 250 mL bottle.

A further 100 mL of the contents of the 750 mL bottle are added to an inertized 500 mL reactor with stirring (400 rpm) and heated to 77° C. The contents of the 250 mL bottle are then transferred into the reactor and the remaining contents of the 750 mL bottle (about 100 mL) complete the filling of the reactor. The reactor is degassed under vacuum until gas bubbles form and then pressurized to 3 bar with the ethylene/butadiene mixture at an 80/20 mole ratio.

When the desired amount of monomer has been consumed, the reactor is degassed. Functionalization is performed with two equivalents of 4,4′-bis(diethylamino)benzophenone (DEAB) relative to the total amount of magnesium, dissolved in toluene.

The medium is stirred for 1 h at 77° C. and then cooled and deactivated with ethanol. The polymer is dried under vacuum at 50° C. for 24 h and then weighed.

About 2 g of polymer are dissolved in 20 mL of methylcyclohexane, and the polymer is then precipitated from about 150 mL of acetone. The operation is repeated three times in succession to wash the polymer. The washed and dried polymer is recovered for analysis.

Example EBR5

The synthesis of the telechelic polymer is similar to that performed in the preceding example EBR3, except that 1.15 mL (0.5 mmol) of 1,5-di(magnesium bromide)pentanediyl prepared according to Example 1 (0.43 mol L⁻¹ in toluene) are used as co-catalyst to prepare the catalytic solution. 10 g of the target monomers are consumed after 129 min of polymerization. 9.50 g of polymer are actually recovered.

Example EBR6

The synthesis of the telechelic polymer is similar to that performed in the preceding example EBR3, except that 0.58 mL (0.25 mmol) of 1,5-di(magnesium bromide)pentanediyl prepared according to Example 1 (0.43 mol L⁻¹ in toluene) are used as co-catalyst to prepare the catalytic solution.

10 g of the target monomers are consumed after 105 min of polymerization. 10.06 g of polymer are actually recovered.

The conditions for the copolymerization of ethylene and 1,3-butadiene are given in Table 3. The catalytic activity expressed in Kg·mol⁻¹·h⁻¹ is measured for each example at 80 minutes of polymerization and is shown in Table 3. The characteristics of the synthesized copolymers are shown in Table 4 and in Table 5. The THF-SEC method was used for polymers EBR2 and EBR4, the HT-SEC method was used for polymers EBR1, EBR3, EBR5 and EBR6. The degree of functionalization, which is defined as the mole ratio of functions bound to the polymer chain per mole of polymer, was calculated by ¹H NMR and using the molar mass of the polymer determined by the THF-SEC method. The microstructure of the polymers was determined by NMR. The ethylene unit content, the 1,3-butadiene unit content in the 1,2-configuration (1,2-unit), in the 1,4-configuration (1,4-unit) and the 1,2-cyclohexane unit content (ring unit) are expressed as molar percentages relative to the total monomer units of the polymer.

Results:

The results show that the use of an organomagnesium reagent in accordance with the invention such as DBMP allows the synthesis of telechelic polymers by polymerization of an olefin such as ethylene or a 1,3-diene such as 1,3-butadiene, and also by their copolymerization. The telechelic nature is shown in particular by marking the polymer ends by reaction with deuterated methanol (PE1M). The telechelic nature is high, considering the content of labelled polymer (Table 2, degree of labelling: 89%) and the average number of deuterated ends per polymer chain (Table 2, labelled end per chain: 1.78 for a theoretical value of 2).

TABLE 1 Mg/Nd Activity mole Protic Time (kg Polymer Co-catalyst ratio compound (min) mol⁻¹h⁻¹) PE1M DBMP 173 MeOD 49 118 PE1NF DBMP 173 MeOH 49 118

TABLE 2 Degree of Labelled M_(n)NMR M_(n) SEC Chain labelling end Polymer (g mol⁻¹) (g mol⁻¹) Ð end (%) per chain PE1M 1630 1480 1.14 D 89 1.78 PE1NF 1630 1530 1.14 H —

TABLE 3 Modifying Activity at Mg/Nd agent or 80 min mole protic Time (kg Polymer Co-catalyst ratio compound (min) mol⁻¹h⁻¹)) EBR1 DBMP 54 MeOH 175 66 EBR2 DBMP 28 DEAB 127 67 EBR3 DBMP 40 MeOH 175 64 EBR4 DBMP 35 DEAB 110 96 EBR5 DBMP 20 MeOH 129 101 EBR6 DBMP 10 MeOH 105 153

TABLE 4 M_(n)SEC Chain Mol % chain Polymer (g mol⁻¹) Ð end end EBR1 8280 1.12 H N/A EBR2 8470 1.18 [N(CH₂CH₃)₂] 0.3 EBR3 13600 1.37 H N/A EBR4 13520 1.18 [N(CH₂CH₃)₂] 0.2 EBR5 20000 1.44 H N/A EBR6 35620 1.65 H N/A

TABLE 5 Ethylene 1,2 1,4 Ring Polymer unit unit unit unit EBR1 75.9 8.6 5.2 10.3 EBR2 79.3 5.1 4.1 11.5 EBR3 75.9 8.5 5.0 10.6 EBR4 79.9 4.4 3.7 12 EBR5 75.9 8.8 5.2 10.1 EBR6 76.0 8.9 5.3 9.8 

1. A catalytic system based at least: on a metallocene of formula (Ia) or (Ib), on an organomagnesium reagent of formula (II) as co-catalyst, {P(Cp¹)(Cp²)Y}  (Ia) Cp³Cp⁴Y  (Ib) Y denoting a group including a rare-earth metal atom, Cp¹, Cp², Cp³ and Cp⁴, which are identical or different, being chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted, P being a group bridging the two groups Cp¹ and Cp² and comprising a silicon or carbon atom, X—Mg—R^(A)—Mg—X  (II) R^(A) being a divalent aliphatic hydrocarbon-based chain, interrupted or not with an oxygen atom, a sulfur atom or with an arylene group, X being a halogen atom.
 2. The catalytic system according to claim 1, in which Cp¹ and Cp² are identical and are chosen from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula C₁₃H₈.
 3. The catalytic system according to claim 1, in which the symbol Y represents the group Met-G, with Met denoting the rare-earth metal atom and G denoting a group comprising the borohydride BH₄ unit or denoting a halogen atom chosen from the group consisting of chlorine, fluorine, bromine and iodine.
 4. The catalytic system according to claim 3, in which G denotes a chlorine atom or the group of formula (III) (BH₄)_((1+y))-L_(y)-N_(x)  (III) in which L represents an alkali metal chosen from the group consisting of lithium, sodium and potassium, N represents a molecule of an ether, x, which may or may not be an integer, is greater than or equal to 0, y, which is an integer, is greater than or equal to
 0. 5. The catalytic system according to claim 1, in which the rare-earth metal is a lanthanide, the atomic number of which ranges from 57 to
 71. 6. The catalytic system according to claim 1, in which the bridge P corresponds to the formula ZR¹R², Z representing a silicon or carbon atom and R¹ and R², which are identical or different, each representing an alkyl group comprising from 1 to 20 carbon atoms.
 7. The catalytic system according to claim 1, in which the metallocene is of formula (III-1), (III-2), (III-3), (III-4) or (III-5): [Me₂Si(Flu)₂Nd(μ-BH₄)₂Li(THF)]  (III-1) [{Me₂SiFlu₂Nd(μ-BH₄)₂Li(THF)}₂]  (III-2) [Me₂SiFlu₂Nd(μ-BH₄)(THF)]  (III-3) [{Me₂SiFlu₂Nd(μ-BH₄)(THF)}₂]  (III-4) [Me₂SiFlu₂Nd(μ-BH₄)]  (III-5) Flu representing the C₁₃H₈ group.
 8. The catalytic system according to claim 1, in which R^(A) is a branched or linear alkanediyl, cycloalkanediyl or xylenediyl radical.
 9. The catalytic system according to claim 1, in which R^(A) contains from 3 to 10 carbon atoms.
 10. A process for preparing a first telechelic polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in claim 1, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.
 11. The process for preparing a second telechelic polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in claim 1, this polymerization step being followed by a step of functionalization with a modifying agent, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.
 12. The process for preparing a polymer, which comprises a step of polymerizing a monomer M in the presence of a catalytic system defined in claim 1 and a termination reaction with a protic compound, the monomer M being chosen from the group of monomers consisting of 1,3-dienes, ethylene, α-monoolefins and mixtures thereof.
 13. The preparation process according to claim 10, in which the monomer M is ethylene or a mixture of a 1,3-diene and ethylene or else a mixture of a 1,3-diene, ethylene and an α-monoolefin, the 1,3-diene advantageously being 1,3-butadiene, isoprene or mixtures thereof.
 14. A telechelic polymer of formula (IV) X—Mg-poly-R^(A)-poly-Mg—X  (IV) in which R^(A) and X are defined according to claim 1, the name “poly” denotes a polymer chain of a 1,3-diene, of ethylene or of an α-monoolefin, or mixtures thereof.
 15. The telechelic polymer according to claim 14, in which the polymer chain contains ethylene units, 1,3-butadiene units and cyclic units, 1,2-cyclohexane units of the following formula


16. The catalytic system according to claim 1, in which the metallocene is of formula (Ia).
 17. The catalytic system according to claim 2, in which Cp¹ and Cp² each represent an unsubstituted fluorenyl group of formula C₁₃H₈.
 18. The catalytic system according to claim 4, in which N represents a molecule of diethyl ether or tetrahydrofuran.
 19. The catalytic system according to claim 4, in which the rare-earth metal is neodymium.
 20. The catalytic system according to claim 4, in which R¹ and R² each represent a methyl. 